1. Field of the Invention
The present invention relates to a light-emitting diode (LED), particularly a method for controlling color contrast of a multi-wavelength LED.
2. Description of the Prior Art
Given the advantages of low power consumption, long service life and diverse features, semiconductor white-light-emitting-diodes (WLEDs) have become a center of attention. Using phosphor, commercialized WLEDs generally convert violet light or blue light photons emitted from indium gallium nitride/gallium nitride (InGaN/GaN)-based multi-quantum-wells (MQWs) into long-wavelength light for white light mixing.
However, the use of phosphor leads to several drawbacks: Stokes-wave energy loss, shorter device lifetime and patent restrictions. By stacking InGaN/GaN-based MQWs of different indium (In) compositions or thicknesses, visible lights of diverse wavelengths are emitted to mix into white light. Based on this rationale, a highly efficient, single-chip, InGaN/GaN MQW WLED can be achieved. Nevertheless, relatively short-range hole migration in InGaN compounds means that the quantum well (QW) nearest to the p-type layer in a light-emitting diode (LED) structure becomes the main source of light emission, thereby making it difficult to control color contrast of multi-color LEDs.
To meet the needs for controlling color contrast of multi-color LEDs, the present invention discloses a method for controlling color contrast of a multi-wavelength LED.